In recent years, with the progress of industrial fields such as electronic parts, batteries, printing and liquid crystal displays, there is an increasing demand for dispersions prepared by dispersing functional particles in a solvent. Further, it has been vigorously attempted to develop dispersants capable of dispersing particles with a polarity on a surface thereof, such as pigments, in a non-aqueous solvent such as an organic solvent.
For example, when pigments are dispersed in an organic solvent by using the dispersants, it is possible to obtain anon-aqueous pigment dispersion. Color filters used in liquid crystal displays are produced by a lithographic method in which a colored composition prepared by compounding a resin, etc., into the non-aqueous pigment dispersion, is applied onto a transparent substrate such as glass, and then successively subjected to exposure to light, curing, development and heat curing, and the like. As the in-oil dispersant used for producing the nom-aqueous pigment dispersion, there are known polymeric dispersants such as graft polymers. In order to satisfy various performances as required, studies on improvement of the dispersants have been made.
For example, Patent Literature 1 aims at achieving both of a good dispersibility of a pigment in a dispersion and a good coatability of the dispersion by improving a wettability (affinity) between the dispersing medium and a surface of the pigment, and discloses a pigment dispersion including a polyurethane-based dispersant containing a structural unit having an ethyleneoxide chain and a propyleneoxide chain, and an amino group quaternarized by a quaternarizing agent.
Patent Literature 2 aims at facilitating removal of dried aggregates generated upon coating, and discloses a pigment dispersion including a block copolymer containing an amino group that partially forms a salt with an allyl halide and/or an aralkyl halide.
Patent Literature 3 aims at satisfying a high optical transparency, a high concentration of a composition, and a good coatability thereof, and discloses a colored resin composition including a binder resin and an A-B block copolymer and/or a B-A-B block copolymer which contain a block A containing a quaternary ammonium salt group on a side chain thereof and a block B containing no quaternary ammonium salt group.